When I swap bitcoin ($BTC) with Liquid ($L-BTC) with a custodial swap service (e.g., CoinOS.io) , I don't "send BTC from Bitcoin to Liquid", ... I send my BTC to the swap service and the swap sends to me their L-BTC.

Even if I peg-in, I'm not technically "sending from Bitcoin to Liquid", ... I'm causing my BTC to be locked and that action causes an equivalent amount of L-BTC to be issued.

It's important to use the correct vocabulary, otherwise you have situations like what happened today (with the hack of Wormhole [ETH]<-->[SOL] bridge) where people holding "ETH tokens on Solana" find they actually only held ETH IOU tokens on Solana, and today those IOUs were worth a whole lot less than 1.0 ETH (until Wormhole said they secured funding to make all IOU tokens whole, ... 1:1 with ETH, once again).